Power clamps are known of the type in which a fluid motor actuated reciprocating movement is adapted to be translated into a swinging movement of a clamp arm attached by an additional linkage or other force transmitting means to the end of a piston rod of the fluid motor. Normally, in the retracted position of the fluid motor, the clamp is in released position, that is, the clamp arm is removed from the work supporting surface and by, means of fluid pressure, the clamp arm is pivotally moved into operating, i.e., clamping position to clamp a workpiece to a work supporting surface, and securely hold the workpiece thereagainst by means of fluid pressure in the fluid motor.
Various guide and linkage means have been proposed to correctly translate reciprocating movement of a piston and piston rod to correct swinging movement of a clamping arm into or out of clamping position, seeking to obtain the highest mechanical advantage which can be utilized within the power stroke of the fluid cylinder. All of these known mechanisms, more or less, include complex designs of various mechanical components at high manufacturing and assembly costs.
Clamps of this type are shown in Applicant's U.S. Pat. Nos. 4,620,696; 4,570,914; 4,496,138; 4,021,027; 3,702,185; 3,618,931; and No. 3,545,050. Each of these clamps has a hollow clamp body axially aligned with and connected to the cylinder and mounted upon a first support, wherein the body is open at the top, bottom and front and includes a pair of opposed, spaced side plates with their one ends out-turned and secured to the cylinder. The opposed sides of the clamp arm cooperatively and guidably bear against interior portions of the body plates during movements between workpiece clamping and release positions. The open design of the hollow body allows entry of dirt and/or other foreign matter into the interior of the body, which can create problems with the internal working mechanisms of the power operated clamp. In addition, the internal mounting of the clamp arm limits the flexibility of readily adapting the clamp for different angular orientations with respect to the clamping position. Disassembly of the entire body is generally required in these clamps to replace the clamp arm with another arm having the desired angular form.